The present invention relates to a musical tone synthesizing apparatus for use in an electronic musical instrument, and more specifically relates to the musical tone synthesizing apparatus of the type utilizing a comb filter having a plurality of resonance peaks for producing desired frequency components of the musical tone from an input signal containing various frequency components.
For example, there has been known the conventional musical tone synthesizing apparatus having a loop circuit including a delay element to constitute a comb filter having a plurality of resonance peaks and being receptive of a white noise signal to selectively filter desired frequency components so as to form a musical tone. Such a type of the musical tone synthesizing apparatus is disclosed, for example, in Japanese patent application publication No. 19354/1984. Generally, the white noise signal contains very low frequency components close to DC. When the white noise signal is continuously fed to the comb filter composed of the loop circuit set with a given delay time for a long time, the looped very low frequency component of the same polarity is repeatedly accumulated to thereby exceed a processing limit so that the loop circuit may overflow, thereby causing a problem such as to fail generation of the musical tone.